Hybrid automatic repeat request (HARQ) is widely supported in current state-of-the-art wireless communication standards. Under automatic repeat request (ARQ), error detection information is added to data before transmission, ensuring that the receiver is able to decode the data. With HARQ, additional forward error correction (FEC) bits are also added to the data.
Several wireless communication standards are defined by the Institute of Electrical and Electronics Engineers (IEEE), including 802.16e (broadband wireless access) and 802.16m (advanced air interface standard). IEEE 802.16e is referred to herein as “802.16e” or “broadband wireless access standard”; IEEE 802.16m is referred to herein as “802.16m” or “advanced air interface standard”.
During a HARQ operation, the HARQ feedback channel is used. A schematic depiction of the differences between the two standards for the HARQ feedback channel is depicted in FIG. 1. The HARQ feedback channel carries either a positive acknowledgement (ACK) or a negative acknowledgement (NACK), depending on the decoding result of the data burst. For the 802.16e broadband wireless standard, the HARQ feedback channel is known as ACKCH 10. For the 802.16m advanced air interface standard, the HARQ feedback channel is known as the HARQ feedback control channel 20 when transmitted in the uplink, and the HARQ Feedback A-MAP (HF-A-MAP) 30 when transmitted in the downlink.
In the current 802.16m standard, the advanced MAP (A-MAP) carries unicast service control information. Unicast service control information consists of user-specific control information and non-user-specific control information. User-specific control information is further divided into assignment information, HARQ feedback information, and power control information, transmitted in the assignment A-MAP 32, HARQ feedback A-MAP 30, and power control A-MAP 36, respectively, as depicted in FIG. 2. The HARQ feedback A-MAP 30 is the HARQ feedback channel under 802.16m in the downlink (FIG. 1). Non-user-specific control information is transmitted in non-user-specific A-MAP 38.
There is a set of HARQ feedback channel resources allocated and one method is needed to specify how to associate the HARQ feedback channel with the data burst, known as HARQ feedback channel indexing.